The present invention relates to a gas-liquid separator that separates unreacted excess hydrogen discharged from a cell stack and product water from each other in a fuel cell system.
A typical fuel cell system has a gas-liquid separator located between the hydrogen outlet and the hydrogen inlet of the cell stack. Unreacted excess hydrogen and product water discharged from the cell stack are separated by a gas-liquid separator, so that the unreacted hydrogen is recovered to the cell stack and reused. The product water is discharged to the outside.
Conventionally, for example, Japanese Laid-Open Patent Publication No. 2006-49100 discloses such a gas-liquid separate used in such a fuel cell system. That is, as shown in FIG. 9, the gas-liquid separator 111 has ion-exchange resin 112 and a tank 113 located below the resin 112. As the fuel cell system starts operating, hydrogen and product water discharged from the hydrogen outlet of the cell stack are conducted to the gas-liquid separator 111 through a circulation passage 114. The hydrogen and product water are separated at the ion-exchange resin 112, and the hydrogen is sent to the cell stack to be reused through a circulation passage 115. The separated product water is received in the tank 113, and discharged to the outside when a discharge valve 116 is open.
In the gas-liquid separator of Japanese Laid-Open Patent Publication No. 2006-49100, the discharge valve 116 is located below the tank 113 so that product water in the tank 113 can be discharged. When the fuel cell system is stopped, product water collected on the inner walls of the case of the gas-liquid separator 111 and product water remaining in the ion-exchange resin 112 drips and is stored in the tank 113. When the fuel cell system is in the stopped state under a low-temperature environment, for example, in winter, such product water in the tank 113 may be frozen. In such a case, even when the fuel cell system is activated, the frozen water may hinder the opening and closing of the discharge valve 116, and discharge of product water to the outside may be impossible. In some cases, the frozen water may damage the discharge valve 116.